Hydrogen storage in underground salt caverns
Underground storage of hydrogen is required for the hydrogen industry to reach large scale. While there are different types of underground storage in development, today salt cavern storage is being used to store thousands of tonnes of hydrogen gas at different sites around the world. The salt that forms the walls of these caverns has low permeability, keeping the hydrogen stored securely underground where it can be recovered on demand. Storing hydrogen in purpose-built salt caverns has an advantage over using depleted gas fields, in that there is no methane contamination.
Geoscience Australia conducted assessments into the suitability of underground salt for hydrogen storage in Australia and found multiple locations potentially suitable for salt cavern construction, including the lesser known Polda Basin on the Eyre Peninsula in South Australia. This small sedimentary basin was discovered in 1968 and since then only 3 wells have been drilled in the offshore part of the basin. While no hydrocarbons were discovered during drilling, the deepest well (Mercury 1) noted high levels of salt in its drilling report. The team at Geoscience Australia searched through their archives at the Geoscience Australia Repository and found small fragments of rock (cuttings) preserved from the 1982 drilling of the well. These were tested and confirmed the presence of salt rock, predominantly halite. Together with digitisation and interpretation of old well logs and historical seismic surveys, Geoscience Australia determined that the salt in the Polda Basin was reasonably extensive, thick and at depths potentially suitable for underground hydrogen storage. It is currently unknown how close to the shore the salt extends (possibly even onshore) due to the limited coverage of seismic and wells in this part of the basin. Modelling by Geoscience Australian suggested that if thick salt is present onshore, it is likely it could be detected using airborne gravity surveys.
Geoscience Australia’s research on salt caverns for hydrogen storage was a key trigger for technology development company entX seeking and receiving gas storage exploration tenements over the Polda Basin (onshore section) and initiating an active exploration program. The exploration program is focused on geological and geophysical studies, with a commitment to drill a well in each of the two licence areas. The program specifically relates to the investigation of salt accumulations in the basin, to consider their suitability for hydrogen storage.
This work could significantly bolster the potential for large-scale hydrogen project developments in the region, by reducing geological risks regarding the presence and extent of salt in the Polda Basin.
A model showing a typical configuration of an underground salt cavern, created by injecting water into an thick underground accumulation of salt rock and dissolving out the salt over a period of years. For underground hydrogen storage, the salt rock must be predominantly halite (sodium chloride) with small amounts of non-salt inclusions.
Image courtesy of Geoscience Australia.
Further reading:
Bradshaw, M., Rees, S., Wang, L., Szczepaniak, M., Cook, W., Voegeli, S., Boreham, C., Wainman, C., Wong, S., Southby, C., Feitz, A. (2023) Australian salt basins – options for underground hydrogen storage. The APPEA Journal 63, 285-304., https://dx.doi.org/10.1071/AJ22153
Wang, L., Rees, S., Carr, L.K., Feitz, A.J. 2023. Feasibility of underground hydrogen storage with salt caverns in the offshore Polda Basin, South Australia. RECORD: 2023/005. Geoscience Australia, Canberra. https://dx.doi.org/10.26186/146489
Dunne, J., Wang, L., PoudjomDjomani, Y., Feitz, A. 2023. Integrated geophysical modelling for salt mapping in the Polda Basin, South Australia. Geoscience Australia, Canberra. https://dx.doi.org/10.26186/148625
Case study: December 2024
HyResearch record: Western Eyre Green Hydrogen Storage